Title

Authors

Document Type

Article

Publication Date

1985

DOI

10.1111/j.1365-246X.1985.tb05164.x

Publication Title

Geophysical Journal of the Royal Astronomical Society

Volume

83

Issue

1

Pages

215-237

Abstract

Summary. From 1977 March 21 to 1981 July 28, about 15 earthquakes with Ms ≥6.0 and many earthquakes with Ms≥4.5 have occurred in Iran. The upsurge of seismic activity started following the Khorqu earthquake of 1977 March 21, M,=7.0, south-east of the Fars folded series of Zagros. This shock had a thrust focal mechanism solution indicating the general northward movement of the Arabian plate with respect to the Iranian landmass. It was followed by six major damaging earthquakes in eastern Iran. The earthquakes are associated with extensive faulting which surrounds the Lut plate. (1) The Zarand earthquake of 1977 December, Ms=5.8, was associated with about 20 km of fault trace, severe mass wasting and about 20cm of right lateral movement. (2) The Tabas earthquake of 1978 September, Ms=7.7, with about 75 km of multiple thrust faulting and a maximum vertical displacement of 35cm. (3) The Kurizan earthquake of 1979 November, Ms=6.0, with more than 17 km of strike-slip fault trace and a maximum right-lateral displacement of 90cm and a vertical displacement of 60cm. (4) The Koli earthquake of 1979 November, Ms=7.1, with at least 65 km of fault trace and a maximum left-lateral displacement of 255 cm and a vertical displacement of 380cm. (5) Golbaf earthquakes of 1981 June, Ms=6.0 with at least 16 km of observed fault trace and a maximum vertical displacement of 15 cm. (6) The Chaharfarsang-Sirch earthquake of 1981 July, Ms=7.1, with about 70 km of discontinuous fault trace and 20cm of right-lateral motion and 15 cm of vertical motion. Portable networks of seismographic stations were deployed following each event. Results of aftershock studies are compared with field observations. The observed faults and aftershock zones appear to mark the broad deformational boundaries of the Lut plate.